org.apache.flink.table.types.inference

Interface InputTypeStrategy

All Known Implementing Classes:

OrInputTypeStrategy, SequenceInputTypeStrategy, VaryingSequenceInputTypeStrategy, WildcardInputTypeStrategy

@PublicEvolving
public interface InputTypeStrategy

Strategy for inferring and validating input arguments in a function call.

This interface has three responsibilities during the TypeInference process:

It can help in resolving the type of untyped NULL literals.

It validates the types of the input arguments.

During the planning process, it can help in resolving the complete DataType, i.e., the conversion class that a function implementation expects from the runtime. This requires that a strategy can also be called on already validated arguments without affecting the logical type.

Note: Implementations should implement Object.hashCode() and Object.equals(Object).

See Also:

InputTypeStrategies

Method Summary

Modifier and Type	Method and Description
ArgumentCount	getArgumentCount() Initial input validation based on the number of arguments.
List<Signature>	getExpectedSignatures(FunctionDefinition definition) Returns a summary of the function's expected signatures.
Optional<List<DataType>>	inferInputTypes(CallContext callContext, boolean throwOnFailure) Main logic for inferring and validating the input arguments.

Method Detail

getArgumentCount

ArgumentCount getArgumentCount()

Initial input validation based on the number of arguments.

inferInputTypes

Optional<List<DataType>> inferInputTypes(CallContext callContext,
                                         boolean throwOnFailure)

Main logic for inferring and validating the input arguments. Returns a list of argument data types that are valid for the given call. If the returned types differ from CallContext.getArgumentDataTypes(), a casting operation can be inserted. An empty result means that the given input is invalid.

Parameters:

callContext - provides details about the function call

throwOnFailure - whether this function is allowed to throw an ValidationException with a meaningful exception in case the inference is not successful or if this function should simply return an empty result.

Returns:

three-state result for either "true, same data types as arguments", "true, but arguments must be casted to returned data types", or "false, no inferred data types could be found"

See Also:

CallContext.newValidationError(String, Object...)

getExpectedSignatures

List<Signature> getExpectedSignatures(FunctionDefinition definition)

Returns a summary of the function's expected signatures.

Parameters:

definition - the function definition that defines the function currently being called.